What the Anesthesiologist Should Know before the Operative Procedure

Excision and grafting for burn injury

Excision and grafting of burn injuries may involve anything from the smallest routine operation to a tour de force involving the participation of a large team of caregivers.

Very small burns may heal by themselves or not need urgent care. At some point, especially when the burn is threatening the homeostasis of the body, surgery may have to be undertaken as soon as possible. If practical, before proceeding to operate, preoperative problems need to be stabilized, as a burn may ultimately affect many organ systems. The burn may also involve other trauma to the body, the treatment of which may take priority.

Vascular access should be achieved and fluid resuscitation following a recognized protocol should be started as soon as possible after the injury. If cardiovascular instability is anticipated, urinary, arterial, and central venous catheters are indicated.

Burn patients need to have their airways assessed immediately after the injury. Smoke inhalation alone may result in airway damage requiring respiratory support. Thermal damage to the airway can also occur in the absence of surface burns in the airway area. Any burn involving the face and neck may compromise the airway due to swelling. Even burns on more than 25% TBSA (total body surface area) remote from the face may jeopardize the airway due to generalized edema formation.

Fiber-optic bronchoscopy should be used to help diagnose airway damage if there is any question about the need to intubate. Delaying intubation when airway support is thought to be necessary may result in airway obstruction and may require dealing with a very difficult intubation later.

What is the risk of delay in order to obtain additional preoperative information?

Small burns that may eventually need surgery can be cleaned and dressed to await surgery scheduled for a later date. Larger burns (size estimated with the use of burn diagrams or the "Rule of Nine") will need fluid resuscitation to stabilize the patient during the period of edema formation. There are various formulas (e.g., Parkland Formula), based on percentage of surface area burned, for quantifying the amount of liquid to be given to the patient over the first 24 hours: one-half should be given over the first 8 hours and the other half over the next 16 hours.

Early excision of burns and provision of care in a specialized burn center have been shown to result in lower morbidity and mortality. Burns that are causing a decrease in blood flow to the extremities or causing an increased intra-abdominal pressure – therefore, compromising ventilation or organ blood flow – will need fasciotomies immediately to relieve pressure.

Emergent surgery: Emergent surgery is usually performed when there is compromised blood flow due to tissue swelling. Immediate surgery is crucial to limit the damage to the tissues at risk. There may be little time to fully evaluate existing conditions. The strategy is to treat problems that arise, while surgery is being performed simultaneously. Often, a fasciotomy may be done in the emergency department or ICU, with the patient heavily sedated.

Vasopressors may be required to maintain blood pressure. After that period, a hyperdynamic state develops with an increased cardiac output (provided there is no hypovolemia) and decreased SVR. In all likelihood, the patient will have decreased body temperature because of heat loss during the intervening time. Therefore, active warming and prevention of further heat loss should be a high priority.

Urgent surgery: Two to three days after the burn injury, the cardiovascular system should stabilize, with regard to fluid shifts. However, other complications may begin to appear. Pulmonary edema, renal failure, and, later, infection may develop. During this time, pre-existing medical conditions should be addressed.

Elective surgery: Elective surgery most often involves excision of very small burns or revision of scars. Patients who have had grafting with a skin substitute will usually need to have it removed and the area covered by autograft. Although not truly elective, autografting of the burn can usually be delayed for a short time if other problems need to be resolved.

Patients with very small burns (<1% TBSA) may have developed some tolerance to opiates if patients have used opiates before. Patients with extensive scarring from major burns may be taking large doses of opiates or may have recently been weaned from them. In either case, the doses of opiates needed for post-operative pain control will need to be carefully evaluated.

Removing nonviable tissue will be necessary, as it will become a source of infection. Covering the excised areas with a skin substitute or skin graft (split skin thickness) will ameliorate infection and allow the tissue bed to begin to heal. These coverings will also decrease evaporative heat loss.

Good vascular access to keep up with the loss of intravascular volume from edema formation and surgical fluid loss is mandatory. During the first 2 to 4 days, the patient may have myocardial depression and increased pulmonary and systemic vascular resistance (PVR and SVR, respectively).

2. Preoperative evaluation

Routine medical clearance is a common cause of delay and may not be necessary in patients with small burns. Patients with minor abnormalities, per the American Heart Association/American College of Cardiology (AHA/ACC) Guidelines, may proceed to surgery with attention to these medical conditions perioperatively. Minor abnormalities include hypertension (HTM) and congestive heart failure (CHF) issues.

Percutaneous coronary interventions (PCIs) prior to surgical interventions have not shown a reduction in adverse cardiac events. In some instances, PCIs have resulted in increased incidence of perioperative events, potentially due to the risk of restenosis and thrombosis if antiplatelet therapy is not utilized, as would be the case with larger burns.

Medically unstable conditions warranting further evaluation include myocardial ischemia, unstable arrhythmias, stroke/TIA, seizure, renal failure, diabetic ketoacidosis, bronchospastic lung disease, drug withdrawal, and coexisting trauma. Some of these may have played a part in the etiology of the burn.

Stabilization of medical problems should be balanced against the risk of delaying the surgery.

3. What are the implications of coexisting disease on perioperative care?

It is often difficult to obtain information about current medications and coexisting disease in burn patients, especially in patients who have very large burns. These patients may have been sedated and intubated before anyone has a chance to take a history.

There is a moderate incidence of burns in patients with psychiatric illness or alcoholism who are also not able to provide a history. Contacting sources for patient medical information may be challenging in these cases but should continue until satisfactory data is obtained. It may necessary to proceed to surgery using tests of suspected disease.

Pre-existing medical conditions may become very important as the severity of the burn increases. Large burns stress most organ systems in the body.

b. Cardiovascular system

Perioperative evaluation

Acute/unstable conditions

- The requirements of the cardiovascular system increase significantly as the size of the burn increases. The heart may be depressed during the early stages of a burn and require pressor support to maintain adequate blood pressure and cardiac output. After the first few post-burn days, the body requires increased cardiac output to match metabolic demands. This usually results in increased heart rate. SVR often decreases at this stage, such that vascular tone will need pharmacologic assistance. In the setting of rapid changes in intravascular volume and increased work load for the heart, any tendency toward CHF, arrhythmias, or myocardial ischemia may be potentiated. Assessment of ischemia, cardiac output, and ventricular filling pressures becomes vital. It is not uncommon that new atrial arrhythmias may develop.

- As burn size increases, changes in sympathetic stimulation, fluid balance, and myocardial depression make early admission to an intensive care unit (preferably, one dedicated to burns) prudent. All of the laboratory and monitoring capabilities available (CVP; arterial pressure; cardiac output; urine output; ultrasound; myocardial scan; ABG, including HGB, ionized Ca++, Mg++, oximetry, and body-environment temperature) may be necessary to manage these patients closely.

Perioperative risk reduction strategies

Monitoring, as outlined earlier, is utilized both for diagnosis and treatment.

Goals: Optimize myocardial oxygen supply-and-demand ratio

- Supplemental oxygen to maintain oxygen saturation.

- HGB maintenance. There may be hemodilution as intravascular volume is increased because of vasodilatation and fluid resuscitation.

- Heart rate: Reduce excessively high rates with calcium channel or beta blockers, keeping in mind that a higher than normal cardiac output may be physiologically necessary and that these patients may develop pulmonary edema at lower filling pressures than normal (due to increased capillary permeability and lower plasma oncotic pressure).

- Avoid hypothermia or hyperthermia. Erring on the side of mild hyperthermia is most practical as patients are susceptible to cool and dry environments. Burned skin is not capable of vasoconstriction to prevent heat loss. After excision, burned surfaces may allow for evaporative heat loss, as may moist dressings.

c. Pulmonary

The presence of coexisting pulmonary disease in burned patients is particularly serious because there will be an increase in oxygen demand and production of carbon dioxide. In addition, there may be an inhalation injury compromising pulmonary function. Patients who have extensive burns, severe facial burns, or need mechanical ventilation will often be intubated before arrival at the hospital. During the course of hospitalization, patients with larger burns may develop pneumonia, pulmonary edema, bronchospasm, and acute respiratory distress syndrome (ARDS).

Perioperative risk reduction strategies

Re-evaluate the usefulness of current medications and consider a nebulized bronchodilator if there is evidence of bronchoconstriction.

Work toward the cessation of smoking in smokers.

Use incentive spirometry.

Consider regional technique.

Have a low threshold for intubating if using general anesthesia.

Intubate with the patient deeply anesthetized and fully relaxed if the airway is manageable

Use inhalational technique if bronchospasm is present and there is cardiovascular stability.

Institute PEEP if beneficial.

Adjust I:E ratio to allow for adequate expiratory phase.

For the patient with a large dead space in the setting of increased carbon dioxide production, permissive hypercapnea may be necessary.

Consider a larger EET for ease of suctioning if there is a respiratory injury or pneumonia.

Perioperative evaluation

Same as above, and an evaluation of which medications were effective in treatment of asthma.

Perioperative risk reduction strategies:

Same as that for COPD.

Consider deep extubation for patients with small burns. Patients with large burns often have high opiate levels and will tolerate the ETT when awakening.

d. Renal-GI:

Patients with small burns and normal renal function will not require any special evaluation. As the burns get larger, there is a risk of inadequate fluid resuscitation. Some deep burns may cause myoglobinuria, which can result in kidney damage. As the size of the burn increases, the greater the caloric intake required to keep up with the metabolic demands. This may require parenteral nutrition or a feeding tube.

Perioperative evaluation

As dehydration may result in renal damage and cardiovascular instability, volume status should be assessed. Urine output, serum BUN, creatinine, and sodium need to be measured.

Hemoconcentration may result from intravascular dehydration. Hemoglobin level should be evaluated with this in mind as anemia may be masked.

Myoglobinuria may result from muscle damage from the burn or a subsequent compartment syndrome. (High voltage electrical burns can cause deep burns with extensive damage to muscle.) Serum or urine myoglobin should be measured if there is any suspicion of muscle damage. Adequate hydration to maintain a high urine output and intravenous sodium bicarbonate may minimize renal injury. Mannitol and furosemide may be beneficial but decrease the utility of using urine output to assess hydration.

Patients with chronic renal insufficiency will be particularly at risk for renal injury.

Perioperative risk reduction strategies

Rehydrate using the most practical criteria available. Most patients with large burns should have a central venous catheter until they are stabilized and no longer require extensive tissue excision.

Place a large bore IV for induction of general anesthesia in patients with large burns, and be prepared to treat hypotension with vasoactive drugs.

e. Neurologic:

Burn patients may have a neurological condition that played a part in the cause of the burn. Baseline neurological status as well as evidence of a new neurological event should be investigated.

Acute issues:

A transient ischemic attack, stroke, hypoglycemia, or seizure may have placed the patient in a position to become injured. Carbon monoxide may impair neurological function.

Perioperative evaluation

A precise history, either from the patient or, if the patient is incapacitated, from a knowledgeable source, should be sought. A witness to the event can be helpful. Obtain lab work to evaluate for substance abuse, blood glucose, and carbon monoxide level. Are there any risk factors for acute neurological issues? If time permits, further testing (CT, MRI, EEG, carotid ultrasound) may be helpful.

Perioperative risk reduction strategies

Depending on the extent of the burn and the necessity for immediate surgery, an ischemic event may require anticoagulation, angiography, or blood pressure control. Antiseizure medication and close monitoring of glucose should be instituted in the appropriate patient. Immediate treatment of carbon monoxide poisoning (with oxygen or hyperbaric oxygen if available) is a high priority.

Chronic disease

Motor or sensory deficits often put a patient at risk for a burn.

Perioperative evaluation

History and physical examination for neurological abnormalities should be done. Are there any spine or chronic pain issues?

Perioperative risk reduction strategies

Maintain blood pressure to assure adequate cerebral perfusion pressure. Evaluate optimal patient positioning. Adjust pain medications to the patient's tolerance. Regional anesthesia can be considered if the patient does not have a wound infection.

f. Endocrine:

Diabetes can effect wound healing, potentiate infections, cause neuropathies, and become unstable in burn patients. Patients with adrenal insufficiency may not be able to mount a stress response to burns.

Acute issues

Prediabetics may develop unstable blood glucose levels, as many patients are in need of parenteral nutrition. Adrenal insufficiency may appear as a low blood pressure response.

Perioperative evaluation

Elicit any history of abnormal blood glucose measurements.

Perioperative risk reduction strategies

Monitor blood glucose levels and treat with insulin when necessary. Test adrenocortical function if there is unexplained hypotension.

Psychiatric

There is a significant incidence of psychiatric issues in the burn patient population. Patients' abnormal behavior may have put them at high risk for burn injury.

Acute issues

The patient may have acute depression, a drug overdose or withdrawal (including alcohol), was accidentally burned, or may have attempted suicide.

Perioperative evaluation

- If the patient is able to communicate, a psychiatric history including medications should be taken. In the event of a noncommunicative patient, every effort should be made to contact a witness or knowledgeable source. Check blood levels for any suspected medications or substances.

Perioperative risk reduction strategies

- Use psychotherapy or the appropriate medications as advised by a consultant. Institute suicide precautions if indicated. Investigate the interactions of any drugs or substances with anesthesia.

Chronic disease

The patient may have stopped or changed his or her medications.

Perioperative evaluation

- Evaluation is the same as evaluation of acute issue, and there may be more information available for mental health providers, friends, or relatives.

Perioperative risk reduction strategies

- Same as acute issues.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

N/A

4. What are the patient's medications and how should they be managed in the perioperative period?

Patients may be taking medications that are vital to their health and need to be continued. Substitutes for oral medications may need to be administered for patients unable to use the GI route. Medications with a long duration of action my need to be replaced with those with a shorter duration.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Burns, even without complications, commonly have a significant impact on the cardiovascular (including blood clotting), respiratory, and endocrine systems. When burn patients take medications that affect these systems, some modification of the regimen will often be necessary.

i. What should be recommended with regard to continuation of medications taken chronically?

Cardiac

- The types of medications being taken for ischemic heart disease will usually need to be continued or modified. If anything, the need for these medications will increase as the heart will have a higher demand for oxygen under the stress of a burn. There are many varieties of antihypertensive medications that can be used, but, often, burn patients are relatively vasodilated, making treatment easier. Anticoagulant-antiplatelet drugs for valves, stents, and PVD may have to be substituted with drugs with a much shorter duration of action if bleeding will interfere with burn surgery (heparin).

Pulmonary

- Patients taking bronchodilator medications may need to continue them, especially if there is respiratory injury associated with the burn. It is relatively easy to administer nebulized formulations to most of these patients, even intraoperatively.

Renal

- The most common drug seen in this category is furosemide. Furosemide is easily intravenously titrated; the clinician should keep in mind its effects on the use of urine output as an indicator of organ perfusion.

Neurologic

- There are antiseizure medications in intravenous form. Keep in mind that sedative drugs may potentiate antiseizure medications.

Psychiatric

- The need for drugs in this area is relatively common in burn patients. As these drugs may have potentiating effects on the sedative/pain/anesthetic medications used on burn patients, psychopharmacology consultation is warranted.

j. How to modify care for patients with known allergies -

When a patient is allergic to a medication, substitute medication with a different structure but similar action.

k. Latex allergy- If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.), prepare the operating room with latex-free products.

N/A

l. Does the patient have antibiotic allergies - Common antibiotic allergies and alternative antibiotics

N/A

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia

Documented. Avoid all trigger agents such as succinylcholine and inhalational agents.

- General anesthesia. Propofol/nitrous oxide/narcotic plus nondepolarizing agent for intubation if needed. In the opiate tolerant patient who will need pain coverage post operatively, a baseline dose of long-acting narcotic initially followed with a fentanyl or remifentanil drip may work well. Ketamine and benzodiazapines are also safe. Monitoring end tidal carbon dioxide and temperature are essential.

- Local anesthetics are not triggering agents. Use local anesthesia or regional anesthesia if appropriate for the particular operation.

- Have MH treatment drugs and protocol in close proximity to the operating room.

Family history or risk factors for MH: Follow procedure for documented risk.

Central core disease, multiminicore disease, nemaline rod myopathy.

5. What laboratory tests should be obtained, and has everything been reviewed?

The laboratory tests to be obtained preoperatively will vary with the extent of the burn and the medical condition of the patient. A young healthy patient with a very small (<1% TBSA) probably does not need any tests. As the complexity of the patient increases, more patient-specific testing will be needed, even in the simplest operations. When it is anticipated that the patient may lose enough blood to need a transfusion, the following laboratory work is warranted:

- For blood loss of more than 1 to 2 liters, whole blood mitigates the loss of serum proteins. Otherwise, packed red blood cells are sufficient. For larger blood loses, a repeat coagulation panel can be a guide for the use of fresh frozen plasma, and a platelet count can guide the decision to transfuse platelets.

Electrolytes

- Potassium in patients on potassium-wasting diuretics or dialysis

- Sodium in dehydration

- BUN/Creatinine in patients with kidney disease or dehydration

- All of the above in patients with significant comorbidities; surgery during the resuscitative period, when more than 1 to 2 liters of blood loss are expected; or for fascial excisions, where there may be a large proteinaceous volume loss with minimal red blood cell loss.

EKG and chest X-ray in patients with significant comorbidities or when a large fluid loss (>1 to 2 liters) is expected.

Intraoperative Management: What are the options for anesthetic management, and how do I determine the best technique?

The choice of type of anesthetic for excision and grafting depends on a variety of factors such as: size, depth and location of the burn and donor sites (if autograft), condition of the patient, and patient position.

For small burns of less than 5% TBSA, when there are no contraindications and the patient is agreeable, a regional anesthetic can be an excellent choice. There may be less immediate postoperative pain and good patient satisfaction.

At the other extreme is the patient with a 90% TBSA burn who is already intubated and septic. This patient is most likely distraught but already well sedated, has a controlled airway, may experience large fluid shifts and blood loss, abnormal coagulation, an unstable blood pressure, and be at risk of infection at a regional site. General anesthesia in this case affords more control of variable factors, such as patient emotional state, movement, ventilation, and overall comfort.

A word about how patients should be transported to the operating room is warranted. The uncomplicated patient with a small burn may be a same-day surgery candidate and have routine transport to the operating room, except in the case of recently administered parenteral opiates. While it is best to have a patient pain free on arrival in the operating room, prior opiate administration may require some level of observation.

If at a level of larger burn size and higher complexity, the patient will need skilled medical practitioners to assist in transport and in monitoring arterial, EKG, and oxygen saturation. Everything that can be done to stabilize the patient before the movement should be organized. Intubated patients may be managed most effectively with sedation and mechanical ventilation.

Simplification of all IV lines prior to arrival in the operating room allows for more attention to the patient's condition. (Many of these patients can be managed with just two lines, an arterial catheter with transducer and a multiport CVP with either an IV solution or a connected transducer. Necessary medications may be infused with the IV solution or CVP transducer flush; and if the patient has a volume requirement, it can be maintained with the IV solution.)

Moving the patient to the operating table can be uncomfortable. Thus, it may be desirable to induce general anesthesia or heavy sedation before the move. During this time, it may be efficient to remove dressings. There should be no shortage of manpower to move the patient: one person guarding the airway, another taking care of the lines, and as many as it takes to handle the patient. Exiting the operating room should be done in the same fashion, although there may be a greater IV volume requirement.

The setup of the operating room for relatively small burn operations is routine. As the size and complexity of burn increases, so do the requirements for safe anesthesia and surgery.

Regional anesthesia:

Neuraxial, peripheral, and field nerve blocks may be used alone or in conjunction with general anesthesia in selected patients. These may be especially useful for decreasing immediate post-operative pain and in opiate-tolerant patients.

Neuraxial

Drawbacks

- Cannot be used in patients with a clotting abnormality, burns to the injection site, and a bacteremia (particularly using an epidural catheter); it may not cover all of the operative sites, and long operations may require significant sedation. High-level blocks may cause vascular instability, particularly during acute blood loss. In the case of an epidural, local anesthetic dose may be limited when fluid containing these drugs is also being administered by the surgeon. Duration of action may be longer than desired, particularly in a transient patient. Requires a cooperative patient.

Peripheral nerve block

Benefits

- Relatively small quantity of anesthetic required, high patient acceptance, little sedation needed with many patients, long duration of action decreases need for opiates, can be used for postoperative pain relief in conjunction with a general anesthetic, and the common donor site of the anterior thigh is often well blocked by femoral nerve block.

Drawbacks

- Nerve damage in unskilled hands, bleeding at site in patients with abnormal clotting, cannot be done through an infected site, many burns not localized to one nerve distribution, and requires a cooperative patient.

Field block

Often used with saline at the donor site to facilitate harvesting of skin however, it has a short duration of action.

Benefits

- The patient may need little or no sedation. They can leave the operating room entirely pain free, and respiration is usually not an issue in patients without severe respiratory disease. It can be used in a patient with a difficult airway.

General anesthesia

Benefits

- Can eliminate patient movement reliably, less distraction by patient concerns, more control of ventilation, can be used for surgery on any area of the body, no limit on duration, additional lines can be inserted without patient discomfort, does not require cooperative patient, less patient discomfort during long operations, secure airway control of ventilation

Drawbacks

- Loss of airway; potential period of instability during induction and wake up; aspiration; vasodilation may lower core temperature and increase heat loss to environment; position injuries; postoperative delirium; requires careful titration of opiates, particularly in tolerant patients; the potency of muscle relaxants and the kinetics of medications may be less predictable than in nonburn patients (low serum protein, high cardiac output, high metabolic rate, neuromuscular receptor changes); and there is the danger of inadvertent succinylcholine administration (hyperkalemic cardiac arrest).

Airway concerns

- Many patients with small burns and no contraindications can have general anesthesia with an laryngeal mask airway (LMA). As the burn size increases, patients will need higher minute ventilation and more opiates. At some point, the patient will need to remain intubated post operatively in order to protect the airway in the face of sedation and pain control. The patient with facial swelling and/or burns or respiratory injury may need to be kept intubated. Securing the endotracheal tube will require an alternative to tape. Ties or Velcro going around the head are solutions. Unplanned extubation of these patients can be a rapidly fatal complication. Care must be taken to re-evaluate the tube position when the patient is becoming edematous and as the edema subsides.

Monitored anesthesia care

This is usually only appropriate for small burns or dressing changes. It can be especially difficult in the opiate tolerant patient as it may take multiple doses to titrate to comfort. Low-dose ketamine can be an alternative.

6. What is the author's preferred method of anesthesia technique and why?

What prophylactic antibiotics should be administered?

The preferred prophylactic antibiotic for burn surgery is cefazolin or cefuroxime. If the patient is at high risk for MRSA use vancomycin. For a beta-lactam allergy, use vancomycin or clindamycin. Burn patients are at risk for infection as long as they have open wounds. Patients in the hospital for prolonged periods are at risk of becoming infected by antibiotic resistant organisms. Antibiotics for these organisms are tailored to the specific organisms. UTILIZE CURRENT SCIP RECOMMENDATIONS WITH DATE OF DETERMINATION of SCIP recommendations.

Surgical approaches: What do I need to know?

Nonviable burned tissue is removed during surgery. The amount removed determines the requirements for anesthesia. Small burns may only need a small amount of debriding and would not be expected to require much need for fluid or blood. If the burn is to be covered with autograft, the tissue harvest site will usually be painful.

As burn surface area increases, the debridement or excision can be expected to lose more fluid through bleeding or weeping of interstitial tissue. This involves using a cutting blade parallel (tangential excision) to the surface to remove nonviable tissue. The dissection continues to remove deeper tissue until there is bleeding at the site. Nonviable tissue has no circulating blood; therefore, when bleeding begins, no more dissection is necessary at that area.

The bleeding sites are cauterized until bleeding stops. The tangential excision has an obligatory blood loss that can easily outpace the fluid replacement. In large excisions, it is often best for the surgeon to cauterize small areas and stop the bleeding before going on to the next area. Bleeding can be minimized by applying tourniquets on extremities, topical epinephrine solutions and/or surface clotting augmentors, and immediate short-term bandaging.

As the depth of the burn increases to include dermis and fat, a fascial excision is done, removing all tissue down to the fascia. The blood loss with this type of excision is usually much less than with the tangential. If fascia or muscle needs to be removed, there will be some additional blood loss. During the edematous phase of the burn, a large amount of fluid loss may occur with a fascial excision. Avoiding hypotension will enable the surgeon to assess the depth of the nonviable tissue. Keeping the patient warm will facilitate clotting.

What are the common intraoperative complications that may occur and how can they be avoided and/or treated?

Hypotension: A common complication is hypotension due to inadequate fluid replacement. It is often difficult to quantify the loss and one must use all of the indicators available: urine output, CVP, hematocrit, weighing sponges, and examining the drapes for accumulations of blood.

The hypotension from hypovolemia must be differentiated from that of general anesthesia. Patients with significantly large burns who have been stable before arrival in the operating room and seemingly normovolemic, may, upon induction of general anesthesia, experience a decreased SVR and become hypotensive with a corresponding decrease in CVP. This condition can usually be treated with a low-dose pressor. A volume infusion at this time may ameliorate the drop, bearing in mind that during emergence, the patient may appear hypervolemic. Patients whose wounds have become infected may become septic during excision. This may not be readily apparent during acute blood loss.

Hypothermia: Hypothermia can often occur rapidly unless precautions are taken. The skin in the burned areas is not able to vasoconstrict, and there can also be considerable evaporative heat loss from moist dressings or body surfaces. Further, the patient may lose heat during transport to the operating room if he or she is inadequately insulated.

The operating room temperature should be elevated before the patient arrives. It is not unusual to need temperature at well over 100Ä F to keep the patient normothermic. It is best to begin the operation with the assumption that the patient's temperature will drop. If it does not, then the temperature of the room may be decreased.

All fluids, including those injected by the surgeon, should be warm. The patient should be covered as much as is practical during the operation. The use of radiant heat lamps may also be useful. Before leaving the operating room, the patient should be thoroughly covered.

Infection: Transmission of pathologic organisms to the patient can be an intraoperative complication, although infection may not be discovered until a later time. Burn patients may have some degree of immunosuppression and may have central intravenous catheters. There may be multiple infusions requiring frequent access. Some lines may have stopcocks. Each invasion of the lines presents an opportunity for contamination. Likewise, patients are often infected with resistant organisms which, without exceptional care, can spread to the environment and other patients. (Infections do not spread by themselves but are spread by our actions.)

Pain: Many burn patients develop a tolerance for opiates and sedating drugs, which creates the potential for anxiety and severe pain during emergence. Avoiding these problems may require administering multiple doses close to the end of surgery and during emergence. The doses required may be of a different degree of magnitude than those for nontolerant patients.

Pulmonary: Respiratory emergencies during burn surgery can be difficult to manage. The face and airway may be edematous. If the face is burned, the surface may be moist or covered with dressings, making it difficult to maintain an adequate mask seal during ventilation.

Patients with respiratory burn and/or who have been intubated for an extended period and/or have had pneumonia may have copious secretions. These secretions may interfere with ventilation, especially if they are thick.

Securing the endotracheal tube in a patient who has an edematous or burned face can be challenging. Complicating this, during the initial days after the burn, swelling of the face may cause the endotracheal tube to gradually slide out of the trachea.

Patients with larger burns have a higher than normal oxygen consumption and will desaturate rapidly if inadvertently extubated or have an interruption of adequate ventilation. Oxygen saturation also decreases in patients who have significant shunts and experience a decrease in cardiac output. If these patients are to be extubated, the extubation must be done in an environment where the dangers of reintubation are minimized, the extent of airway edema can be evaluated, and where the patients can be closely monitored. Burn patients in whom the management of pain is difficult may need to remain intubated until they are comfortable and adequately ventilating.

Coagulopathy – hemorrhage: Low levels of clotting factors, platelets, or hypothermia may result in difficulty in controlling wound bleeding, particularly during tangential excisions

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

N/A

c. Postoperative management

Analgesia

The primary agents for analgesia are opiates. Patients undergoing operations that are expected to have postoperative pain should be given as much long-acting opiate as is practical before emergence. Patients with opiate tolerance may require significant quantities when they awaken. In these cases, it is advisable to avoid drugs with long onset of action (morphine). If the patient has been on a long-term fentanyl infusion preoperatively, fentanyl may be the reasonable choice since its duration of action will be sufficiently prolonged.

Extubation

Patients who remain intubated postoperatively and are expected to remain that way for a day or more, should be admitted to an ICU setting (preferably one with a staff that is familiar with burn patient needs) with full monitoring and ventilator assistance. Patients who are extubated in the operating room and require large doses of opiates should be admitted to a post-anesthesia care unit (PACU) with close monitoring of respiratory status. Extubated opiate-naive patients can go to a PACU and transferred home or to a floor bed when their pain and respiratory status is stable.

Postoperative complications

Pain: Inadequate treatment of pain before emergence can result in significant postoperative discomfort that may take considerable time to treat. Early planning of opiate administration is necessary.

Pulmonary edema: Careful monitoring of intraoperative fluid needs and prevention of sudden blood and filling pressure increases after emergence will decrease the risk of pulmonary edema.

Delirium: The use of anxiolytics and pain medication at the first sign of delirium will minimize the severity.

Hypoxia-atelectasis : Intraoperative suctioning of bronchial secretions and using a mechanical ventilator with PEEP to maintain adequate tidal volumes during the entire course of the operation and transport to a postoperative unit will optimize respiratory function.